Heat exchanger plenums for go-karts

ABSTRACT

Heat exchanger systems for go-karts include a heat exchanger and a plenum that channels air to the heat exchanger to increase cooling efficiency while reducing drag. The plenum has an intake with an area less than a cross-sectional area of a portion of the plenum where the heat exchanger is located to allow velocity air pressure to decrease while increasing static air pressure. The plenum and heat exchanger may be located at various sites on the go-kart including in front of the driver position, beside the driver position, and behind the driver position. Additionally, a centrifugal fan may be included in the plenum to increase the velocity air pressure to overcome internal losses. Also, a plenum body portion may be included on the rear side of the heat exchanger to channel air away from the heat exchanger.

TECHNICAL FIELD

The present invention is related to heat exchangers for go-karts withliquid cooled engines. More particularly, the present invention isrelated to plenums that work in conjunction with the heat exchangers ofthe go-karts.

BACKGROUND

Go-karts are a popular form of recreation and competition. Go-karts arethose vehicles having four wheels, a frame, and an open cockpit but lacka suspension system. While go-karts started with air-cooled engines,high-performance go-karts have progressed to liquid-cooled engines thatutilize a liquid-to-air heat exchanger to remove the heat from theliquid. This liquid cooled configuration allows the engines to achieve ahigher performance without overheating.

The heat exchangers, such as a radiator, receive airflow as the go-karttravels, and the heat of the liquid is transferred through the heatexchanger to the flowing air. Typically, go-karts have a side-mountedheat exchanger that is exposed to the surroundings as go-karts areusually limited in size, and the side mount is a convenient place toposition the heat exchanger. Thus, air is directed at and around theside-mounted heat exchanger to provide the cooling. However, thisconventional side-mounted heat exchanger is an aerodynamicallyinefficient design.

The aerodynamic inefficiency of this side-mounted heat exchanger occursbecause the heat exchanger creates drag by providing resistance to theair passing by the go-kart. Additionally, the side-mounted and exposedposition of the radiator provides only a limited amount of air pressureon the front surface of the radiator. Thus, the heat exchanger must notbe dense so that air with only limited pressure can be satisfactorilyforced through, but must be relatively large to achieve the necessaryamount of cooling due to the lack of density. The relatively large sizeof the heat exchanger results in an overly large amount of drag. Thisdrag created by the heat exchanger negatively impacts the performance,namely acceleration and top speed of the go-kart and therefore, is anundesirable result.

Attempts have been made to improve upon the side-mounted heat exchanger.For example, heat exchangers have been mounted on the rear of thego-kart. However, a rear-mounted heat exchanger also generates anunacceptable amount of drag. This unacceptable amount of drag occursboth because of the blunt, non-aerodynamic shape created by the heatexchanger at the rear of the go-kart and also because the heat exchangermust be relatively large with a low density to account for the lack ofair pressure developed on the front side of the heat exchanger.

Attempts have also been made to increase the cooling efficiency of therear-mounted heat exchanger. A plenum has been placed on the front-sideof the rear-mounted heat exchanger to channel air since the rear-mountedheat exchanger is behind the driver seat and does not otherwise receivea freestream of airflow. However, these attempts have failed to properlymatch the plenum to the heat exchanger to optimize static air pressureon the front of the heat exchanger such that the rear-mounted heatexchanger must continue to be large with a relatively low fin density.Furthermore, these attempts have failed to address the drag associatedwith the blunt shape at the rear of the go-kart due to the presence ofthe heat exchanger. Thus, the drag associated with a heat exchanger fora go-kart continues to negatively impact performance.

SUMMARY

Embodiments of the present invention address these issues and others byproviding a heat exchanger system for a go-kart that includes a heatexchanger and a plenum body that channels air to the heat exchanger.Utilizing the heat exchanger system allows improved cooling efficiencywhile decreasing drag. The heat exchanger and plenum body may be placedin various locations on the go-kart. Additionally, an additional plenumbody portion may be included to channel air away from the heatexchanger.

One embodiment is heat exchanger system for a go-kart. The heatexchanger system includes a body defining an intake opening on a firstend of the body and a portion having a cross-sectional area larger thanan area of the intake opening such that the body defines an expansionchamber between the intake opening and the portion. The first end of theplenum body is adapted to face toward the direction of travel of ago-kart. The heat exchanger system also includes a heat exchangerpositioned in proximity to the portion of the body such that the bodychannels air from the intake opening to the heat exchanger. The velocityof air decreases as it approaches the heat exchanger while passingthrough the expansion chamber thereby decreasing velocity pressure ofthe air and increasing static pressure of the air. The air pressure atan entry to the heat exchanger resulting from the body is matched to apressure loss of the heat exchanger by having a cross-sectional area ofthe portion equal to 4.2 times the area of the intake.

Another embodiment is a heat exchanger system for a go-kart. The heatexchanger system includes a body defining an intake opening on a firstend of the body and a portion having a cross-sectional area larger thanan area of the intake opening such that the body defines an expansionchamber between the intake opening and the portion. The first end of theplenum body is adapted to face toward the direction of travel of ago-kart. The heat exchanger system also includes a heat exchangerpositioned in proximity to the portion of the body and adapted to bepositioned in a freestream such that the body channels freestream airfrom the intake opening to the heat exchanger and wherein the velocityof air decreases as it approaches the heat exchanger while passingthrough the expansion chamber thereby decreasing velocity pressure ofthe air and increasing static pressure of the air. The static pressureat an entry to the heat exchanger resulting from the body is greaterthan a freestream static pressure.

Another embodiment is a go-kart that includes a frame and four wheelscoupled directly to the frame such that the four wheels are rigid withthe frame but rotate relative to the frame. A liquid-cooled enginemounted to the frame and a drive linkage is located between the engineand at least one of the four wheels. A heat exchanger is in fluidcommunication with the liquid cooled engine. A plenum body is positionedin proximity to the heat exchanger such that the plenum body channelsair to the heat exchanger, and the plenum body defines an intake openingon a first end of the plenum body and defines a portion having across-sectional area larger than an area of the intake opening such thatthe plenum body defines an expansion chamber between the intake openingand the portion. The velocity of air decreases as it approaches the heatexchanger while passing through the expansion chamber thereby decreasingvelocity pressure of the air and increasing static pressure of the air.The air pressure at an entry to the heat exchanger resulting from thebody is matched to a pressure loss of the heat exchanger by having aratio of the cross-sectional area of the portion to the area of theintake substantially equal to 4.2.

Another embodiment is a go-kart that includes a frame and four wheelscoupled directly to the frame such that the four wheels are rigid withthe frame but rotate relative to the frame. A liquid-cooled engine ismounted to the frame, and a drive linkage is located between the engineand at least one of the four wheels. A heat exchanger is in fluidcommunication with the liquid cooled engine and is mounted in afreestream position. A plenum body is positioned in proximity to theheat exchanger such that the plenum body channels freestream air to theheat exchanger, and the plenum body defines an intake opening on a firstend of the plenum body and defines a portion having a cross-sectionalarea larger than an area of the intake opening such that the plenum bodydefines an expansion chamber between the intake opening and the portion.The velocity of air decreases as it approaches the heat exchanger whilepassing through the expansion chamber thereby decreasing velocitypressure of the air and increasing static pressure of the air. Thestatic pressure at an entry to the heat exchanger resulting from thebody is greater than a freestream static pressure.

Another embodiment is a go-kart that includes a frame including asteering wheel support and four wheels coupled directly to the framesuch that the four wheels are rigid with the frame but rotate relativeto the frame. A liquid-cooled engine is mounted to the frame, and adrive linkage is located between the engine and at least one of the fourwheels. A heat exchanger is in fluid communication with the liquidcooled engine, and the heat exchanger is mounted rigidly with respect tothe frame at the steering wheel support. A plenum is positioned inproximity to and on a direction of travel side of the heat exchangersuch that the plenum channels air to the heat exchanger. The plenumdefines an intake opening on a first side of the plenum body and definesa portion having a cross-sectional area larger than an area of theintake opening such that the plenum body defines an expansion chamberbetween the intake opening and the portion.

Another embodiment is a go-kart that includes a frame including aside-mounted heat exchanger support and four wheels coupled directly tothe frame such that the four wheels are rigid with the frame but rotaterelative to the frame. A liquid-cooled engine is mounted to the frame,and a drive linkage is located between the engine and at least one ofthe four wheels. A heat exchanger is in fluid communication with theliquid cooled engine, and the heat exchanger is mounted to the frame atthe side-mounted heat exchanger support. A plenum body is positioned inproximity to and on the front side of the heat exchanger such that theplenum channels air to the heat exchanger, and the plenum defines anintake opening on a first end of the plenum body and defines a portionhaving a cross-sectional area larger than an area of the intake openingsuch that the plenum body defines an expansion chamber between theintake opening and the portion.

Another embodiment is a go-kart that includes a frame including a seatand a heat exchanger support behind the seat and four wheels coupleddirectly to the frame such that the four wheels are rigid with the framebut rotate relative to the frame. A liquid-cooled engine is mounted tothe frame, and a drive linkage is located between the engine and atleast one of the four wheels. A heat exchanger is in fluid communicationwith the liquid cooled engine, and the heat exchanger is mounted to theframe at the heat exchanger support. A plenum system is positioned inproximity to the heat exchanger and includes a front-side plenum portionthat channels air to the heat exchanger and includes a rear-side plenumportion that channels air away from the heat exchanger.

Another embodiment is a go-kart that includes a frame including a seatand a heat exchanger support and four wheels coupled directly to theframe such that the four wheels are rigid with the frame but rotaterelative to the frame. A liquid-cooled engine is mounted to the frame,and a drive linkage is located between the engine and at least one ofthe four wheels. A heat exchanger is in fluid communication with theliquid cooled engine, and the heat exchanger is mounted to the frame atthe heat exchanger support. A plenum system is positioned in proximityto the heat exchanger and includes a plenum that channels air to theheat exchanger. The plenum system further includes a centrifugal fanwithin the plenum that increases the velocity air pressure of the airchanneled to the heat exchanger.

Another embodiment is a heat exchanger system for a go-kart. The heatexchanger system includes a body defining an intake opening on a firstend of the body and a portion having a cross-sectional area larger thanan area of the intake opening such that the body defines an expansionchamber between the intake opening and the portion. The first end of theplenum body is adapted to face toward the direction of travel of ago-kart. A heat exchanger has a fin density of at least 17 fins per inchand is positioned in proximity to the portion of the body such that thebody channels air from the intake opening to the heat exchanger. Thevelocity of air decreases as it approaches the heat exchanger whilepassing through the expansion chamber thereby decreasing velocitypressure of the air and increasing static pressure of the air such thatairflow is maintained through the heat exchanger.

Another embodiment is a go-kart that includes a frame and four wheelscoupled directly to the frame such that the four wheels are rigid withthe frame but rotate relative to the frame. A liquid-cooled engine ismounted to the frame, and a drive linkage is located between the engineand at least one of the four wheels. A heat exchanger is in fluidcommunication with the liquid cooled engine and has a fin density of atleast 17 fins per inch. A plenum body is positioned in proximity to theheat exchanger such that the plenum body channels air to the heatexchanger, and the plenum body defines an intake opening on a first endof the plenum body and defines a portion having a cross-sectional arealarger than an area of the intake opening such that the plenum bodydefines an expansion chamber between the intake opening and the portion.The velocity of air decreases as it approaches the heat exchanger whilepassing through the expansion chamber thereby decreasing velocitypressure of the air and increasing static pressure of the air such thatairflow is maintained through fins of the heat exchanger.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the airflow and related pressures for a heat exchanger fora go-kart without a plenum body.

FIG. 2 shows the airflow and related pressures for a heat exchangersystem for a go-kart that includes a plenum body.

FIGS. 3 and 4 show a standard go-kart in a top view and side view,respectively, to illustrate the various locations where a heat exchangersystem may be located.

FIGS. 5 and 6 show a go-kart in a top view and side view, respectively,having a heat exchanger system including a front-side plenum and heatexchanger mounted to a steering wheel support of the go-kart.

FIGS. 7 and 8 show the go-kart of FIGS. 5 and 6 in a top view and sideview, respectively, including a driver and show airflow around the heatexchanger system and driver maintaining a substantially laminar flow.

FIGS. 9 and 10 show a go-kart in a top view and side view, respectively,having a heat exchanger system including a front-side plenum and heatexchanger mounted to a side-mount and show airflow through and aroundthe heat exchanger system.

FIGS. 11 and 12 show a go-kart in a top view and side view,respectively, having a heat exchanger system including a front sideplenum portion, a rear side plenum portion, and a heat exchanger mountedto a side-mount and show airflow through and around the heat exchangersystem.

FIGS. 13 and 14 show a go-kart in a top view and side view,respectively, having a heat exchanger system including a front sideplenum portion, a rear side plenum portion, and a heat exchanger mountedbehind the seat and show airflow through the heat exchanger system.

FIGS. 15 and 16 show a go-kart in a top view and side view,respectively, including a driver and having a heat exchanger systemincluding a front side plenum portion, a rear side plenum portion, and aheat exchanger mounted behind the seat and show airflow through the heatexchanger system.

FIGS. 17 and 18 show a go-kart in a top view and side view,respectively, having a heat exchanger system including a front sideplenum portion, a centrifugal fan mounted within the front side plenumportion, a rear side plenum portion, and a heat exchanger and showairflow through the heat exchanger system.

DETAILED DESCRIPTION

Embodiments of the present invention provide a heat exchanger system fora go-kart to improve cooling efficiency and reduce drag to therebyincrease the performance of the go-kart. As opposed to having a heatexchanger alone, embodiments of the present invention provide a plenumbody in conjunction with a heat exchanger. The plenum body channels airto the heat exchanger while providing an aerodynamically efficient shapeto also allow airflow to maintain a laminar flow around the heatexchanger.

As shown in FIG. 1, a heat exchanger 102 of a go-kart directly exposedto airflow 104, i.e. a freestream, causes the airflow to pass directlyinto the heat exchanger 102 while some airflow 106 escapes around theouter edges including the left and right sides and the top and bottom.The airflow 104 that encounters the heat exchanger 102 is restricted bythe flow resistance of the heat exchanger 102 resulting in a build-up instatic air pressure within the region 108. As the air builds in staticpressure, the velocity pressure decreases as the airflow in region 108slightly decreases.

The curve 110 shows the velocity (V) of the airflow relative to the heatexchanger 102, while the curve 112 shows the velocity pressure and curve114 shows the static pressure relative to the heat exchanger. As can beseen in curve 110, the airflow velocity begins to slightly decreasewithin region 108, reaches a minimum as the airflow passes through theheat exchanger 102, and then increases in velocity relative to the heatexchanger 102 after having exited the heat exchanger 102.

The airflow pressure is an important factor in the efficiency of theheat exchanger 102. The airflow pressure is the sum of the velocitypressure (P_(v)) and the static pressure (P_(s)). The change in thestatic pressure as the air passes through the heat exchanger 102reflects most directly upon the efficiency of the heat exchanger 102 forrelatively low velocity, and this static pressure results from thedegree of velocity pressure change as the airflow encounters the heatexchanger 102. The curve 112 demonstrates that the velocity pressure ofthe air also begins decreasing when the velocity begins decreasing,reaches a minimum as the air reaches the heat exchanger 102, and thenincreases to steady state upon the airflow exiting the heat exchanger102. The curve 114 demonstrates that the static pressure is minimaluntil the airflow begins to encounter the heat exchanger in region 108,and then the static pressure begins increasing, peaking as the airreaches the heat exchanger 102, and then decreases from the peak back toa minimal amount as the air passes through the heat exchanger 102.

While the freestream heat exchanger configuration of FIG. 1 does providefor cooling of the go-kart engine, it can be seen that the change instatic pressure through the heat exchanger 102 is a relatively smallamount. Thus, the cooling efficiency of this heat exchangerconfiguration is relatively low. Furthermore, this heat exchangerconfiguration is a relatively inefficient aerodynamic design as theairflow 106 escapes around the sides and may lead to turbulent flow,possibly reverse flow through the radiator further decreasing coolingefficiency, and also increases the drag of the go-kart. Additionally,for rear-mounted heat exchangers, the heat exchanger is not exposed to afreestream such that little to no static pressure builds on the frontside of the heat exchanger.

FIG. 2 shows a heat exchanger system that includes a plenum 220 inconjunction with a heat exchanger 202. A plenum is a body or chamberthat exists at a different pressure than the external surroundings. Inthis application, the plenum provides for a different air pressure atthe heat exchanger than is present outside of the plenum. The airflow204 approaches the heat exchanger system and some of the airflow entersthe plenum 220 at an intake opening 208 on a first end of the plenum220.

As the airflow passes through the plenum toward the heat exchanger, theairflow passes through an expansion chamber 212 created by thecross-sectional area of the plenum 220 increasing as the airflow movesfrom the intake opening 208 to a portion of the plenum 220 where theheat exchanger 202 is located. The increase in cross-sectional areathrough the expansion chamber 212 results in a greater volume to befilled by the airflow which results in a slowing of the airflow as itproceeds through the expansion chamber 212 toward the heat exchanger202.

The velocity and pressure curves demonstrate the effect the plenum 220has to increase the cooling efficiency of the heat exchanger 202. Curve214 demonstrates that the velocity (V) of the airflow begins to decreasesignificantly as the airflow proceeds through the expansion chamber 212,reaches its minimum upon encountering the heat exchanger 202, and beginsto increase as the airflow exits the heat exchanger 202. Curve 216demonstrates that the velocity pressure (P_(v)) begins to decrease withthe velocity of the airflow as the airflow proceeds through theexpansion chamber 212, reaches its minimum as the airflow encounters theheat exchanger 202, and then increases as the airflow exits the heatexchanger 202 and rejoins the freestream. Curve 218 demonstrates thatthe static pressure (P_(s)) substantially increases as the airflowpasses through the expansion chamber 212, reaches its maximum as theairflow encounters the heat exchanger 202, and rapidly decreases back toa minimal amount as the airflow passes through the heat exchanger 202.

The expansion chamber 212 allows the airflow to decrease in velocitymuch more than the velocity decreased for the freestream configuration.While the velocity pressure is reduced much more as well, this allowsthe static pressure to increase to a much higher amount than is achievedin the freestream configuration. This higher static pressure results inhigher cooling efficiency through the heat exchanger 202.

It has been determined that the ratio of the intake area to thecross-sectional area of the portion of the plenum where the heatexchanger is located is a relevant factor to properly build the staticpressure on the front side of the heat exchanger. It has been found thatan optimized ratio of cross-sectional area of the portion at the heatexchanger to the area of the opening is approximately 4.2. It has alsobeen found that a deviation of +/20% of the area of the intake and/or ofthe cross-sectional area of the portion at the heat exchanger achievesan acceptable degree of cooling efficiency improvement over a freestreamconfiguration so long as the ratio remains +/−20% of 4.2, and worksespecially well when applied in conjunction with the heat exchangervalues discussed below. Table 1 below provides a range of theseoperating parameters for one example of a heat exchanger system.

It has also been determined that the fin density of the heat exchangeris a relevant factor. It has been found that an increased fin densityfor the heat exchanger is desirable to increase cooling efficiency for aheat exchanger of a given area, and the fin density may be increased toreduce the size of the heat exchanger when used in combination with aplenum. As with the ratio of the areas discussed above, a deviation of+/20% of the fin density of the heat exchanger has been found to achievean acceptable degree of cooling efficiency improvement over a freestreamconfiguration when applied in conjunction with the plenum ratiodiscussed above. It has been found that a fin density of 17 fins perinch or greater provide for enhanced cooling efficiency when used inconjunction with a properly proportioned plenum.

Table 1 below also provides a range of this operating parameter as wellas an illustrative range for core thickness for examples of a heatexchanger system. It will be appreciated that these ranges are providedas examples only and are not intended to be limiting and that many otherparameters may be manipulated to adjust heat exchanger performance. Suchparameters include tube spacing and orientation, fin orientation, louverpitch, and the materials used.

TABLE 1 optimized dimension +20% −20% intake area  15 (in²) 18 12 heatexchanger  63 (in²) 75.6 50.4 portion cross- sectional area ratio ofportion to 4.2 5 3.4 intake fin density  21 (fin/in) 25.2 16.8 corethickness 1.5 (in) 1.8 1.2

The plenum and heat exchanger may be constructed from one of severaldifferent materials. Plastic, fiberglass, carbon composites, and Kevlarhave been found to be suitable materials for the plenum body. It hasbeen found that a bare duct plenum may be used to achieve an acceptableimprovement in cooling efficiency. However, a plenum having vanes (i.e.,rib-like formations) extending between the intake opening and theportion at the heat exchanger may also be used to further limit flowseparation and frictional losses within the plenum body. Aluminum andcopper have been found to be suitable materials for the heat exchangerto achieve adequate heat transfer from the cooling liquid passingthrough the heat exchanger core to the airflow passing through the heatexchanger.

FIGS. 3 and 4 show typical go-kart 300 having four wheels 304 rigidlyattached to a frame 302 rather than being suspended from the frame 302.The go-kart includes a liquid-cooled engine 306 and includes a drivelinkage 308 that includes an axle between the rear wheels that is linkedto the engine 306 by a chain, belt, or drive shaft. The go-kart includesa seat 310 for the driver and includes a steering wheel 312 and steeringwheel support 322. The steering wheel 312 is linked to the front wheelsthrough a steering mechanism including a steering wheel shaft incombination with tie rods and spindles so that the front wheels can turnwith turning of the steering wheel 312 to change the direction of travelof the go-kart.

The go-kart 300 has several locations where a heat exchanger system maybe located. The heat exchanger system may be placed in front of thedriver at a front area 314 and be mounted to the steering wheel support322. The heat exchanger system may alternatively be placed to one sideor the other of the driver, such as at side area 316, and be mounted tothe frame 302. The heat exchanger system may also be placed behind thedriver at a rear area 318. The various heat exchanger systems andmounting locations are discussed below with reference to FIGS. 5-18.

FIGS. 5 and 6 show a go-kart 500 with a heat exchanger system mounted infront of the driver position. The heat exchanger system includes aplenum body 502 and heat exchanger 506. The plenum body 502 has anopening 504 facing the direction of travel of the go-kart for receivingthe airflow, and the airflow exits from the heat exchanger system outthe rear side of the heat exchanger 506. The expansion chamber 508 ofthe plenum is located between the front opening 504 and the heatexchanger 506. The heat exchanger system is mounted to the steeringwheel support 510.

FIGS. 7 and 8 show a go-kart 700 with the heat exchanger system of FIGS.5 and 7 but the go-kart 700 is shown in motion with airflow 706 andincludes a driver 704. The driver 704 and the plenum 702 form anaerodynamic shape that allows the airflow 706 to maintain asubstantially laminar flow around the shape. As shown, the airflow thatdoes not enter the plenum is channeled around and over the plenum 702and driver 704 to maintain the laminar flow and reduce the dragotherwise produced by a freestream configuration.

FIGS. 9 and 10 show a go-kart 900 with a heat exchanger system mountedto a side of the driver position. A plenum 902 channels airflow 906 to aheat exchanger 904. The airflow 706 exits from the rear of the heatexchanger 904. Airflow 908 that does not enter the plenum 902 maintainslaminar flow as it passes around the plenum 908 and beyond the go-kart900.

FIGS. 11 and 12 show a go-kart 1100 with a heat exchanger system mountedto a side of the driver position that includes both a front side plenumportion 1102 and a rear side plenum portion 1110. The front side plenumportion 1102 directs airflow 1106 to the heat exchanger 1104 while therear side plenum portion 1110 directs airflow 1106 away from the heatexchanger 1104 after the airflow 1106 has passed through the heatexchanger 1104. The airflow 1108 that does not enter the front sideplenum portion 1102 maintains laminar flow as it passes around the frontside plenum 1102 and also around the rear side plenum 1108. The rearside plenum 1108 further assures that the airflow 1108 maintains laminarflow upon passing the front side plenum portion and also eliminates anyturbulent flow leading to the possibility of reverse flow through theheat exchanger 1104.

Additionally, the rear side plenum portion provides the inverse effectof increasing the velocity of the airflow 1106 once it has exited theheat exchanger 1104 to further assure that the static pressure remainsminimal on the rear side of the heat exchanger 1104, thereby furtherenhancing the cooling efficiency. The rear side plenum has a portion atthe heat exchanger 1104 that has a greater cross-sectional area than anarea of the exit opening such that the velocity of the airflow returnsto its maximum value upon reaching the exit opening.

FIGS. 13 and 14 show a go-kart 1300 with a heat exchanger system mountedbehind the driver position that includes both a front side plenumportion 1302 and a rear side plenum portion 1308. The front side plenumportion 1302 has an intake to the side of or above the seat 1310 anddirects airflow 1306 to the heat exchanger 1304 while the rear sideplenum portion 1308 directs airflow 1306 away from the heat exchanger1304 after the airflow 1306 has passed through the heat exchanger 1304.

The rear side plenum portion of this heat exchanger system configurationalso provides the inverse effect of increasing the velocity of theairflow 1306 once it has exited the heat exchanger 1304 to furtherassure that the static pressure remains minimal on the rear side of theheat exchanger 1304, thereby further enhancing the cooling efficiency.The rear side plenum 1308 has a portion at the heat exchanger 1304 thathas a greater cross-sectional area than an area of the exit opening suchthat the velocity of the airflow returns to its maximum value uponreaching the exit opening.

FIGS. 15 and 16 show a go-kart 1500 with a similar heat exchanger systemto that of FIGS. 13 and 14 except that the orientation of the heatexchanger is altered by about 90 degrees, and the go-kart 1500 is shownin motion with airflow 1506 entering the plenum and includes a driver1510. The driver 1510 together with the front side plenum portion 1502on the front side of a heat exchanger 1504 and rear side plenum portion1508 on the rear side of the heat exchanger 1504 form an aerodynamicshape that allows the airflow to maintain a substantially laminar flowaround the shape. As shown, the airflow that does not enter the plenumis channeled around and over the driver 1510, front side plenum portion1502, and rear side plenum portion 1508 to maintain the laminar flow andreduce the drag otherwise produced by a freestream configuration.

FIGS. 17 and 18 show a go-kart 1700 with a heat exchanger system mountedbehind the driver position that includes both a front side plenumportion 1702 and a rear side plenum portion 1708. The front side plenumportion 1702 has an intake to the side of or above the seat 1720 anddirects airflow 1706 to the heat exchanger 1704 while the rear sideplenum portion 1708 directs airflow 1706 away from the heat exchanger1704 after the airflow 1706 has passed through the heat exchanger 1704.

In this example, a centrifugal fan 1710 is located within the front sideplenum portion 1702. As shown, the centrifugal fan 1710 is driven by achain or belt 1714 linked to the drive axle 1716. The centrifugal fan1710 creates turbulent airflow 1712 with an increased velocity relativeto the airflow 1706 entering the front side plenum portion 1702 toovercome frictional losses of the intake opening of the front sideplenum portion 1702 so as to maintain a high airflow velocity andincrease velocity pressure. As the increased velocity pressureexperiences a greater pressure drop when approaching the heat exchanger1704, the static pressure builds to a higher peak pressure before beingdissipated entirely as the airflow 1706 proceeds through the heatexchanger 1704.

In addition to driving the centrifugal fan 1710 from a part of the drivelinkage between the engine and the drive wheel(s), the centrifugal fan1710 may be powered in other manners as well. For example, an electricalmotor may be included to drive the centrifugal fan 1710. The electricalmotor may be battery-powered or may be powered from an electricalgenerator being powered by the engine of the go-kart.

The rear side plenum portion may also be included to provide the inverseeffect of increasing the velocity as the airflow 1706 exits and proceedsaway from the heat exchanger 1704. In the example shown, the airflowexits the rear side heat exchanger at the rear-underside location 1718of the go-kart frame such that the airflow passing underneath thego-kart assists in creating a low pressure that draws the airflow fromthe plenum to further increase the exit velocity.

While the centrifugal fan has been shown and described in relation to arear mounted heat exchanger system that includes both a front sideplenum portion 1702 and a rear side plenum portion 1708, it will beappreciated that the centrifugal fan may be included between the intakeopening and the portion of the plenum where the heat exchanger islocated in any of the various mounting positions described herein. Useof an electrical motor to drive the fan allows placement of the fan inlocations where drive from the drive linkage is not possible.Furthermore, it will be appreciated that the centrifugal fan may beincluded in heat exchanger systems that include a plenum body only onthe front side of the heat exchanger as well as heat exchanger systemsincluding a front side plenum portion and a rear side plenum portion.

Although the present invention has been described in connection withvarious illustrative embodiments, those of ordinary skill in the artwill understand that many modifications can be made thereto within thescope of the claims that follow. Accordingly, it is not intended thatthe scope of the invention in any way be limited by the abovedescription, but instead be determined entirely by reference to theclaims that follow.

1-39. (canceled)
 40. A go-kart, comprising: a frame including a seatthat is exposed to an ambient and a heat exchanger support; four wheelscoupled directly to the frame such that the four wheels are rigid withthe frame but rotate relative to the frame; a liquid-cooled enginemounted to the frame; a drive linkage between the engine and at leastone of the four wheels; a heat exchanger that is exposed to the ambientand that is in fluid communication with the liquid-cooled engine, theheat exchanger being mounted to the frame at the heat exchanger support;and a plenum system positioned in proximity to the heat exchanger andincluding an intake-side plenum portion that channels air to the heatexchanger and including an exhaust-side plenum portion that channels airaway from the heat exchanger.
 41. The go-kart of claim 40, wherein theheat exchanger is positioned to a side of the seat.
 42. The go-kart ofclaim 40, wherein the heat exchanger is positioned behind the seat. 43.The go-kart of claim 40, wherein the heat exchanger has a first sidewith exposed fins that faces a direction other than a direction oftravel provided by the four wheels.
 44. The go-kart of claim 40, whereinthe heat exchanger has a first side with exposed fins that faces adirection of travel provided by the four wheels.
 45. The go-kart ofclaim 40, wherein the intake-side plenum portion defines an intakeopening and defines a first portion having a cross-sectional area largerthan an area of the intake opening and wherein the heat exchanger islocated in proximity to the first portion.
 46. The go-kart of claim 40,wherein the exhaust-side plenum defines a second portion and defines anexit opening having an area smaller than a cross-sectional area of thesecond portion and wherein the heat exchanger is located in proximity tothe second portion.
 47. The go-kart of claim 40, wherein the intake-sideplenum includes a fan.
 48. The go-kart of claim 47, wherein the fan isdriven from the drive linkage.
 49. The go-kart of claim 40, wherein theexhaust-side plenum provides an exit at an area proximate to a rearunder-side of the frame.